Process of producing foraminous sheets



i' De@ 24,` 1940. E Q NQRRIS n 2,226,383

PRocEss oF PRODUCING FoRAMINoUs SHEETS Filed Aug. 31, 1938 2 Sheets-Sheet 1` ff, e J Z4' /a Y INVENTOR ATTORNEY v Dec. 24,1940. E. NoRRls 22265583, Y

PROCESS OF PRDUCING` FORAMINOUS SHEETS n y I Filed Aug. v51. 195e 2 sheets-sheet 2 /f 3,3 y '1g' Lf/ bz j* lf/@w v INVENTOR Y fol/mwa /Voe'o B l n ATTORNEY Y Patented Dec. 24, 1940 vrnooEss 0E raonUcmG EonAMmoUs t snEE'rs y O. NorrisrWestport, Conn., noignorto Edward' 0. Norris, Inc., New York. N. Y.,ia corporationof NewYorkv n u Application Au'rust' 31, lssasensifno. 227,843

..171 claims. (cuoio-'11V Y Theinvention. relates to processes of producing foraxninous sheet is characteriziedt by the fact that it producesy a sheet. the thicknessl of which is" comparatively great as coxriparjedV with the size of the perforations. Y By -way of more detailed explanation, attention is directed to my' United States Patent No. 2,166,367, issued July 18, 1939. In -that'patent I describe a.l matrix for thefelectrodeposltion of screen or other foraminous sheet, the characteristics ofV the matrixv being a, depositingsurface exhibiting a screen patternand insulated vsurfaces of Bakelite or other material having properties similarthere; to so far as resistance to receiving an electrolytic deposit is-concerned. 'Ihe exposed surfaces of the insulated areasof such a matrix are flush, or nearly so, with the deposit recelvingareas. Foraminous sheet elsctrolyticallyk deposited, on and removed from suchv matrixis quite satisfactory ii" only a limitedthickness is required. ,How-` ever, the thickness to whichv therdeposit .may be` built is by :the yfact that,as theI electrolyticdeposition is continued.- the deposit creeps over the insulated areas andthe perforations or holes in thedeposit become smaller andsmaller and,lii` the process iscontinued long enough,v gradually closeupZ entirely. U 0f course, the proc-l ess maybe arrested at any'stage andas stated abovev in eifect,l.the"product will serve many use-` ful purposes. More frequently however foraminous sheet (which fork convenience may termed screen) is desired, in which large per'- forations exist, coupledgwith a thickness'greater than can be produced by arresting the depositing process at thepoint atlvwhich the"v desired hole size has been attained.` Broadly stated, themain object., of the' linvention-is to .enlarge the holes of any screen without fyreducing the but more, particularlyit is to produce screen oi larger hole -size coupled withiigreater thickness than can be produced by fsimply depositing on a matrix of the charactervabove described. .Y

In'the foregoing explanation of theV` nature of my process I have referred toy perfor-ations" or holes" that are to bev enlarged. However, as

will appear. in the Vmo'refldetailed description ofM the process that is to follow. it is not necessary that there beinitially actualholes orperforations extending from face to face of 'the sheet. On thefcontrary, favorable lresults, may be ob-` tained by starting thef'process with a sheet 'that is merely pittedthat is to say.'e. g., a sheet produced by carrying the depositing prcess'to the point at which the lands are contiguous or even merged together, provided pits areleft. Buch a process is where; anextraordinarily thick screen .is iesired,y althoughordinarily it is prefer'- able that the deposit be not carried to the point at whichftheholes are Ventirely closed. Ivwill f f use the. term .recessl to describe both holes and pits. .Y .A 4

Referring'to the drawings, V Flg. ,1.is a plan view of a metallic `screen the holes o f Jwhichare to be enlarged but the thickness ofgwhich is notto be reduced;

Fig. 2is aview on the line 2-2 of Fig. l; f "Figs, 3 andi illustrateuintermediatelsteps in the process, Fig. ll'illustrating the final product;

Figs. 6.17,8, and 9 illustrate theseveralsteps in a modifledform of the process;

Figs. 10,11, 12,. 13, 14, and 15l illustrate the several steps in another'modiiied form of the process: j ,o

Fig. ldillustrates an adaptation of the process to a screen v,the lands of which are` contiguous and even merged together. 1 ,l v o y' Describing more' specifically the 'successive steps illustrated in Figs. 1-5, both inclusive, Fig. l shows a portion of screen produced by'electrodepositionon a matrix of the character hereinabove-described,"comprising the lands lli running in one direction and the connecting lands I I nmning in a direction at right-angles thereto.- For kthe purpose of` describing this form'of the-invention, thematerial of this screen may bev assumedv to be electrolytically deposited copper, and itwill be noticed.that the perirationsy I2 are oik relatively small diameter as compared withv the width1of the connecting lands' Ii. words, the dimension is small as compared `with thev dimensionb-c. Likewise, the thick ness considerable in comparison with'the dimension The dimension a-b will at In f other times be hereinaftergreferred Vto as the hole f size" andthe dimension H as the fland size." 'The -nextv'stepin the process now being described is toy implyA tolbothI faces of'thescreen .coatings i3 and M of some-material vthat can be subjected to treatment that will selectively re-v The screen of Fig. 3 may now be subjected to the action of ferrie chloride which acts destructively on the copper of the screen but does not affect the ink. As an alternative, it may be subjected anodically to electrolytic action. In either case the result is as illustrated in Fig. 4-viz., the walls of the holes have been eaten away as indicated by the numeral II, leaving however the coatings i3 and il overhanging the 4enlarged holes I6. 'I'he final step consists in removing the ink coatings I3 and Il which may be accomplished by applying a suitable solvent, such, for example, as acetone. The result is a screen as shown in Fig. 5.

While I have specified ink of thetype above referred to as a suitable material for carrying out the form of the process now being described, it should be noted that ink is mentioned only as an example, other substances such as Bakelite varnish or tacky shellac being suitable.

In the modified process illustrated in Figs. 6 to 9, both inclusive, the entire surface of the screen, including not only the faces thereof but the walls of the holes as well, are nrst covered with a coating 20 of asphaltum. The asphaltum may even completely ll the holes `as shown in Fig. 6, but this condition does not interfere with the process.

Next, the asphaltum is removed from the faces of the screen by any suitable method such as the abrasive action of sand paper, or av grinding wheel, or the cutting action of steel wool, or by rubbing, and thin layers 2| and 22 of nickel are then electrolytically deposited on the bare areas.

Of course, the walls of the holes being still masked by the asphaltum receive no deposit.

'I'he next step consists in removing the asphaltum that remains in the holes by dissolving in a suitable solvent, such as benzine or benzol.

'Ihe screen of Fig. 7 (the asphaltum being assumed to have been removed as above stated) is then subjected to the action of a suitable agent that reacts destructively on the copper but does not affect the nickel deposit. An example of such an agent is a mixture of chromic and sulphuric acids in water, suitable proportions being about as follows:

Sulphuric acid lbs V 2 Chrornic acid lb- 1 Water l ,.gallons 10 Another agent that may be used forv the purpose is a solution of potassium cyanide. As an alternative, the screen may be subjected anodically to electrolytic action. The result of any one of these processes is the structure of Fig. 8. The nickel, in turn, may be removed by using it as an anode in a ten per cent. solution of hydrochloric acid.

A process somewhat akinto the process first described, but which is not illustrated, may comprise running the screen of Fig. 2 between two opposed gelatin or felt rollers impregnated with gold chloride. The result isa deposit of gold on the faces of the screen by the well-known phenomenon known as replacement." The screen may be then etched with ferric chloride until the lands are reduced the desired amount, and any overhanging areas of the gold may be removed by abrasion or even left on.

The preferred process illustrated in Figs. 10 to 15 comprises first applying to the screen of Fig. 2` a coating 30 of some material that can be subiected to treatmentthat will selectively remove v it without aifecting the material of the screen itself.- A suitable material is chromium which may be applied simply by electrodeposition. Chromium is selected for the reason that it reacts to hydrochloric acid, while copper does not. On the other hand, copper reacts to ferric chloride, While chrome is passive to it.

In the next step illustrated in Fig. l1 the chrome covered faces of the sheetl as indicated at 3i and l2, have been activated-l. e., rendered capable of receiving a deposit of copper. In explanation, it should be stated that I have found that it is very diiiicult, if not impossible, to electrodeposit acid copper or nickel on the surface of an electrodeposit of chromium. To the extent that such a deposit takes place, it is spotty and the surface is far fromcomp1etely covered; on the other hand, the surface of the chromium deposit may be activated so that it will readily take an electrodeposit of acid copper or nickel. The activation may be eifected by rubbing, lightly grinding or abrading the chrome surface. Steel wool or pumice are suitable agents for the purpose. Activation of the faces only of the sheet is effected, the surfaces of the walls of the holes remaining passive. A` chrome deposit of approximately .0002" thick lends' itself to this step in the process very well.

In the next step, illustrated in Fig. 12, the

screen of Fig. 11 is subjected as a cathode to an electrolytic copper bath, the result of which is to apply to the activated chrome areas coatings 33 and u of copper. These copper coatings, as stated above, cover only the activated chrome surfaces and in accordance with what has been said are capable of acting as a protective coatingfor the chrome, such that the chrome may be dissolved by the application of hydrochloric acid, while the copper remains intact.

In the next step illustrated in Fig. i3, the screen of Fig. 12 is subjected to the action of hydrochloric acid, thegeffect of which is to remove the chrome from the walls of the perforations leaving the copper exposed as shown' at l5. As an alternative, the chrome may be de-plated by employing the screen as an anode inl a caustic soda bath of a concentration of from 5 to 10%. But the copper deposit I3 and those portions of the chrome deposit 30 4that are covered by the copper deposit Il are not affected by thehydrochloric acid or by the deplating process, although, of course,..both'cut the chrome slightly under the copper as indicated at Il and 31.

Thescreen of Fig. 13 is now ready for enlarging the perforations, and this is accomplished by subjecting it to the action of a suitable etching agent such as ferrie-chloride, which not only acts destructively to remove :material from the walls of the holes but also removes the protective coatings 33 and Il of copper. K 'I'he chrome, however, is not a'ected by the ferricfchloride, and the resulting product is shown in Fig. 14, the lands being indicated by the numeral 3l and the perforations by thenumeral de. Such of the original chrome deposit, however, asis shown in Fig. 13, still remains, and this maybe' easily removed by submitting the structure of Fig. 14 to the actionof hydrochloric acid.v An illustrative final productis shown in Fig. 15.

The foregoing process (of Figs. 10 to l5) may be carried out by using'nickel in place of chrome.

screen are activated. This maybe done by immersing it in concentrated nitric acid. Thereupon, the nickel on both faces of the screen is activated as describedwith reference to Fig.,.1l and in the same manner as in the caseof chrome,

and thecopper depositillustrated in F18'. 1211s then laid on. fAsanetching agent forrem'oving kthe nickel from the walls of the holes. anodicy treatment in hydrochloric acid hereinbefore ldescribed would be used. The holes would. then be enlarged by subjecting'the screen to -theaction of a solution of chromic `and sulphuric 'acids of about the proportion above given. It is not Y necessary in carrying out the "process described with reference to Figs. 19 to l5 to start with a copper screen. I yIV l o' In describing the process of Figs. y10 to 15, I havenot referred to a nickel screen as the basis of carrying-it out. Howevena' nickel screen may be used in the same manner as a copper screen, Y with theadditional feature that, for .the purpose oi. enlarging the holes, dilute nitric acid could be used as an alternative forv ferric-chloride. An-

other process of accomplishing `the objects of the .invention also involves the initial use of a, nickel screen. `l 'I'he nickel is lfirst rendered passive Ito electrodeposition by immersion .in hot concentrated nitric acid. Preferably the concentration should be as high as possibley and ought to be continued for a sumcient time -for .the nickel to acquire a degree of passivity at which it will not easilyfreceive a deposit. Both surfaces of the screen are then activated by rubbing with pumice, ysteel wool or l other abrasive or cutting agent. This leaves the walls of the holes resistant to a deposit while the surfaces of the screen l.

are receptive to a deposit. Itis then treated l cathodically in an acid copper electrolytic vbath ing within the spirit and scope of my invention,

and the abraded or rubbed surfacesy receive-a` deposit, while thewalls of the holesdo not. The screen can then be subjected to electrolytic deplating in a 10% solution' of hydrochloric acid which results in enlarging the holes without dissolving the, copper. The copper may then. if desired, be removed by an application, of chromic and sulphuric acid of about the proportionshereinabove mentioned.

v Fig. 1e is a view simmer tether or Fui.'sex-ceptY that in Fig. 16 the 'screen is shownwith the lands run together asy shown at 40, completely closing' up the holes but leaving recesses-4I Each of the processes thatvhas been described may be started with a screen of this type aswell as witha screen in which the holes have been left open. However', they only advantage in so doing occurs when it is desired to make ay screen the landslof which are extraordinarily thick as compared with the hole `I `wish to` make clear that in many, ifnot in most cases. the use of chemical reagents on the one hand. and electrolytic deplatlng on thel other,

are simply alternatives and that a person familiar with the art can readily substitute one for the other as occasion requires or permits.

I have described above certain embodiments of my invention and a preferred process with certain modifications thereof, but I wish it to be understood that these are illustrative and not limitative of my invention and that I reserve the right to make various changes in form, construction, and arrangement of parts and also to make various changes in process of manufacture fallas set i'orth in the claims.

I claim:

v 'I'he process o'f enlarging the perforations in foraminous sheet material.without substantially reducing the thickness of the sheet, which corn-k prlses the, steps" or covering tnesurraes ofthe. v:sheet including the walls` of the perforations with aV coating yof material resistantfto an?etehilvig ferent. which isgdestrutivly"reactivate thema?- terial ofthe sheet, then: rendering the'arrea's of coating thatdo not .cover4 the walls of the fper'forations resistant'toasecondetching agent that acts to. `remove ,the remaining material ofv the coating but whichdoes .not react on the' material of the sheetremoving the said vcoating froinzthe walls` ofthe perforations by the action of said second agent,- and. removing thel material of the,

ywalls of theperforations to anextentsufllcientto ,Y n

reduce'the ,width of the andato s. desiree ext nt, bymeans of the `ilrst mentioned agent. f"

Y', 2. 'Thief-process,ofenlarging theholes offorarn-- '2o .inoussneet without substantmuyreducmg the thickness of thesheet. `whichcornprises the steps y. y yof covering the surface ofz-the sheet including. the

walls oifV the holes'with-r awcoating of material resistantf tol a -,dissolving. agent that fdestructively reactsionthe material ofthe sheet, rendering the areas of coating-that do notcoverv the-walls of the 'holes resistant toasecond dissolvingagent thatgacts :to remove -theremaining material yof,

the coatingandwhich doesnot react onthe; material of the sheet',y removing'V the said coating fromfthe walls of-.the`,holesf;by subjectinglthe rf sheet to the actionfof said second` agent. vremoving the material ofthe. wallsof Vthe holes toan y extent suillcient to Lreduce. thewidth of the-lands" .to adesired vextent'by. means of--the first mentioned agent, .and removing `the. vresistant portion ofsaid coating .by a dissolvingagent thatg'does not ailect the material ofthe sheet.

`r3. The process of .enlarginglthe holesgofrforaminous copper sheet. without, substantially ,re-

.the stepsof electroplating thesuri'ace of the cop'- `per ysheet includingwthewalls of the holesy with chromium, rendering the chromium active to electrodeposition of any adherent ,coating of ,cop-

per overcv those .areas that doVR not constitutei the@ `walls. of `vthe lholes. electroplating the saidA kareas 1 with a.v coatingof copper, removing .the chromium from-the .walls ofthe holes -by subjecting'the sheetf'to'the action of. hydrochloric acid, sub- "lectingth'e` sheet tothe action of @ferric-'chloride luntil-the land width'is-reduced to'a desired ex-r tent andthe copper coating isfremoved, andy-"removing the remaining chromium' by subjecting thesheet` to the 'actionof hydrochloricacid.' .i

' 4. The' process of enlargingthe holes of foram'` inous copper sheet without substantially`- reduc.-

ing` the 'f'thiclcness thereof, which comprises :the

steps of electroplating the surface ofthe' sheet including the Walls of the'hqles With'lchromium,

rendering the chromiumactive toelectrode'posi,

the steps of electroplating the surface o f the` 40 'ducingthethickness thereof, which comprises-tl 4 lassesses sheet including the walls of the holes with chromium, rendering the chromium active to electrodeposition of an adherent coating ot copper over those areas that do not cover the walls of the l holes,`electrop1ating the said areas with copper, removing the chromium from the walls' o! the holes by an etching agent that is passive with respect to thecopper, and subjecting the sheet to the action oi a second etching agent that reacts 10 destructively on the'copper but does not aiIect the chromium until the land width is `reducedto a desired extent and the copper coating is removed. Y

6. The process of enlarging the holes of fol i'aminous copper sheetV without substantially reducing the thickness thereof, which comprises the steps of electroplating the surface of the sheet including the walls of the holes with chromium, rendering the chromium active to electrodeposil tion of an `adherent coating of copper over those areas that'do not cover the wallsoi the holes, electroplating the said areas with copper, removing the chromium from the walls of the holes by the action of an etching reagent which acts 2l destructively on the chromium but does not aiIect the copper, and subjecting the sheet to the action of a second etching reagent that acts destructively on the copper but does notaflect kthe chromium until the land width is reduced to a 80 desired extent and the copper coating is removed.

7. The process of enlarging the holes inforaminous metal sheet without substantially reducing the thickness of said sheet, which comprises the steps of rendering the walls of the $5 holes inactive Ato electrolytic deposition and the faces of the sheet active to electrolytic deposition of an adherent metal coat, electroplating the activated areas with a metal resistant to an etching agent which is capable of dissolving the metal 40 of the body of the screen, and subjecting the sheet to the action of such agent for a period of time suiliclent to reduce the width of the lands to a desired extent.

8. The process of enlarging the holes in io- .45 raminous metal sheet with substantially reducing the thickness of said sheet, which comprises the steps of covering by electroplating the surface oi the sheet including the walls of the holes with a coating of a metal passive to electrolytic 5o deposition but capable of .being rendered active to the same, rendering active to electrolytic depl osition of an adherent metal coating those areas of the coating that do not cover the walls o! the holes, electro-plating the activated areas with a 55 metal that is resistant to a given etching agent that destructively reacts on the-coating. removving the uncovered areas of said coating by the application of said agent, and subjecting the sheet to the action of a second etching agent for a period of time sumcient to enlarge the diameters of the holes to a desired extent.

9. 'I'he rocess oi'V enlarging the holes in foraminous metal sheet without substantially reducing the thickness of said sheet, which comprises the steps of electroplating the surfaceoi the sheet including the walls .ot the holes with a second metal capable o1' becoming inactive to electrolytic deposition but capable of being activated to receive such deposition, rendering active to electrolyticdeposition those areas of the second metal that do not cover the walls of the holes, electroplatingthe said activated areas with a metallic coating, selectively removing the un# plated areas ot the said second metal by means of an etching agent that does not aiTect the metal of the sheet or the metallic coating, and then subjecting the sheet to the action of a second'etching agent which destructively reacts on the exposed metal of the sheet and/or the metallic coating for a period of ltime sumcientto reduce the land width toa desired extent and. to remove the said metallic coating.

10.' A process of enlarging the holes in foraminus metal sheet without substantially reducing the thickness of the sheet, which comprises ,thesteps of electroplating the surface o! the sheet including the walls or the holes with a coating of a second metal, the surface of which is passive to` electroly'tlc deposition, which said metal is resistant to the action of an etching agent that destructively reacts on the metal o! the sheet, then rendering the faces of the sheet except the walls of the holes active to electrolytic deposition of an adherent coating ofv metal, then electroplating the active areas with a third metal on which the mst-mentioned agent destructively reacts, removing the second metal from the walls of the holes by means of a second etching agent that does not aiect the ilrst or the third metals, thus leaving the metal of the sheet constituting the walls of the holes exposed, and then subjecting the sheet to the action of the firstmentioned agent for a period of time sumcient to reduce the land width to a desired extent and to remove the said third metal.

l1. The process of enlarging the holes of foraminous copper sheet without substantially reducing thek thickness thereof, which comprises the steps of electroplating the surface of the copper sheet including the walls of the holes with chromium, rendering the chromium active to electrodeposition of an adherent coating of copper over those areas that do not constitute the walls of the holes, electroplating the said areas with a coating of copper, removing the chromiuml from the walls of the holes by subjecting the sheet to the action of an etching agentv that etches chromium but does not affect copper, then subjecting the sheet to the action o1' an'etching agent thatetches copper but does not aiect chromium until the land width is reduced to a desired extent and the copper coating is removed, and then removing the remaining chromium by subjecting the sheet to the action o! an etching agent that etches chromiumbut does not affect copper.

EDWARD O. NORRIS. 

